Submission #1246796

#	Time	Username	Problem	Language	Result	Execution time	Memory
1246796		M_SH_O	Cat Exercise (JOI23_ho_t4)	C++20	100 / 100	235 ms	77548 KiB

Main

/*#pragma GCC optimize("O3")
#pragma GCC optimization("Ofast,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")*/
#include <bits/stdc++.h>
/*#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>*/

#define ll long long
#define ll1 long long
#define ull unsigned long long
#define dou long double
#define str string
#define vll vector<ll>
#define vi vector<int>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vbool vector<bool>
#define vstr vector<str>
#define vvll vector<vll>
#define pb push_back
#define pf push_front
#define endl "\n"
#define fr first
#define se second
// #define sortcmp(a) sort(a.begin(), a.end(), cmp)
#define sort(a) sort(a.begin(), a.end())
#define reverse(a) reverse(a.begin(), a.end())
#define speed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define INF 1000000000000000007
#define ordered_set tree<ll, null_type, less_equal<ll>, rb_tree_tag, tree_order_statistics_node_update>

using namespace std;
//using namespace __gnu_pbds;

mt19937 rng(time(0));
ll randll(ll l, ll r) {
    return uniform_int_distribution<ll>(l, r)(rng);
}

vvll g;

vll p, a;

ll find(ll v){
    if(p[v] == v) return v;
    return p[v] = find(p[v]);
}

void unite(ll a1, ll b){
    a1 = find(a1);
    b = find(b);
    if(a1 == b) return;
    if(a[a1] > a[b]) p[b] = a1;
    else p[a1] = b;
}

vll tin, tout, pref;
vll c;
vvll pr;
ll t = 0;

void dfs(ll v, ll d = 0, ll p = -1){
    c.pb(v);
    for(int i = 0; (1 << i) < c.size(); i ++){
        pr[v][i] = c[c.size()-(1 << i)-1];
    }
    tin[v] = t++;
    pref[v] = d;
    for(int i : g[v]){
        if(i == p) continue;
        dfs(i, d+1, v);
    }
    tout[v] = t ++;
    c.pop_back();
}

bool f(ll a, ll b){
    if(tin[a] <= tin[b] && tout[a] >= tout[b]) return 1;
    return 0;
}

ll lca(ll a, ll b){
    if(f(a, b)) return a;
    if(f(b, a)) return b;
    
    ll x = a;
    for(int i = 19; i >= 0; i --){
        if(pr[x][i] == -1 || f(pr[x][i], b)) continue;
        x = pr[x][i];
        //cout << x << endl;
    }
    return pr[x][0];
}

int main(){
    speed;
    srand(time(0));

    ll n;
    cin >> n;
    a.resize(n+7);
    g.resize(n+7);
    p.resize(n+7);
    tin.resize(n+7);
    tout.resize(n+7);
    pr.resize(n+7, vll(20, -1));
    pref.resize(n+7, 0);
    vpll v;
    for(int i = 1; i <= n; i ++){
        cin >> a[i];
        p[i] = i;
        v.pb({a[i], i});
    }
    
    for(int i = 0; i < n-1; i ++){
        ll a, b;
        cin >> a >> b;
        g[a].pb(b);
        g[b].pb(a);
    }
    dfs(1);
    vll dp(n+7, 0);
    //cout << lca(5, 7) << endl;
    
    sort(v);
    for(auto i : v){
        for(int j : g[i.se]){
            if(a[j] > i.fr) continue;
            ll c = find(j);
            //cout << i.se << ' ' << j << ' ' << c << ' ' << lca(i.se, c) << ' ' << pref[i.se] << ' ' << pref[c] << endl;
            dp[i.se] = max(dp[i.se], dp[c] + pref[i.se] + pref[c] - 2*pref[lca(i.se, c)]);
            unite(j, i.se);
        }
        //cout << i.se << ' ' << dp[i.se] << endl;
    }
    
    cout << dp[v.back().se] << endl;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26